Assessing the Effects of Land-use and Slope Aspects on Soil Phosphorus Fractions: a Comparative Study in Degraded and Naturally Regenerated Forest Ecosystems

Abstract

Abstract Phosphorus (P) is the second most important nutritional element for plant growth and improves the balance of forest soil ecology. In this study, nutrient elements were comparatively evaluated as phosphorus fractions in soil using sequential extraction using a UV-VIS spectrophotometer from typically degraded Hustai and naturally regenerated Udleg, Batsumber. The objective of this study was to assess the effects of different land-use and slope aspects on soil inorganic phosphorus (Pi) and organic phosphorus (Po) fractions with different availabilities. In this study, labile P decreased with decreasing slope in the Udleg plots, whereas nonlabile P and calcium-bound phosphorus (Ca-P) increased with decreasing slope in the Udleg plots. Furthermore, aluminum-bound phosphorus (Al-P) and Ca-P showed no changes by the slopes in the Hustai plots. The contents of nonlabile Po and moderately labile Po in Hustai and Udleg were higher than those of labile Po. The content of nonlabile Po in Udleg soil was significantly higher (t-test, p < 0.001) than in Hustai, which indicates that humic acid-bound P (humic-P) was derived from plants. A high Ca-P content was recorded at the lower forest edge of Hustai.Low-labile Po was derived from organic residues in Hustai and plant residues in Udleg, which were easily mineralized by soil microbes. The incorporation of organic and plant residues in Hustai and Udleg, respectively, increased soil pH, contributing to P availability for plant uptake. Further studies are needed to determine the nutritional elements in plants, evaluate their relationship with the soil, and evaluate their ecological significance.